Electrolytic production of acetylene carboxylic acid



United States Patent LELECTROLYTIC PRODUG'I ION ACETYLENE 4 CARBOXYLICACID ,Viktoi' Wolf; Hamburg,.Germany 'iNo Drawing. Application'July 8,1954, :SerialNo. 442,203

' Claims priority, application Germany July 20,1953

2 Claims. 2 (Cl'i204-79) This invention relates to .theproductionOf-acetylene carboxylic acids.

Various. processes are already knownforthe production J of acetylenecarboxylic acids.

..'Propiolic acid has, fortexample; :beenpreparedby con-;yertingacetylene-with sodium into sodium acetylideaa'ndreactingtzthelatter with CO2 (U.'-S. .specificationwlslo. 2,205,885);alternatively acetylene sis cconverted FWlth chlorinewintotrichlorethylene, thesaid product isi'concompoundsby treatment withalkalimetalsand subsequent carbonisation :is 'mOf subordinateimportance. .'(.Gilman, 'Haubin, J. Amer..Chem.Soc. 67 (1945);:1'420.) 1Similarly, the action of carbon=dioxide onracetylene-di-Grig- A nardcompounds. is. out of the gquestion for, synthesis .on -thetechnicalscale (Ruggli,-Helv..-3 (1920.);559; G-rignard, Lapayre Faki, C. L187(1928), 517). "ThGZCOH- ventional methodat the present time is :toremovehydrogen halide from different halogenated succinic acidszormaleic;or fumeric acids. his true that by this. means a yield of 73-.88%is obtained, but the starting-materials are not readily available:-(Perkin, Simonsen; .lourniliChem.

(Soc- 9.1,(1907), 816; Abbott, Arnold,vThompson, Organic .SyntheseslS(-19 38), .3). It thereforehad to be considered tasxa technicaladvance-when Heilbron and:collaborators .(J. Chem-Soc. .1949, 604) wereable-tooxidise-in sulphide ;solution, by means. of .chromic acid,butin-.(2-)-:'diol.-1.,'4

which is. today available on alargetechnical scale. .HOW- even, theyieldscould not. beincreased toimore than 23% .and .could ,onlybeobtained-by addition of "an vorganic solvent (acetone). According tothe invention acetylene carboxylic acids. are obtained in good yieldby'the electrolytic oxidation inacid solution of an acetylene alcoholwith one or more primary hydroxyl groups, such assbutin- 2) -diol-1,4 orbutin-( l )-ol-4 or propin-,(.1-) -ol=3. T he anode solution can beworked up in manner .known per =se, for'example by extractingwithanorganic solvenwdrying the extract and evaporating the solvent invacuo. This process is of value from a technical point of view, not onlyon account of the cheap oxidising means, but also because it can becarried out with inexpensive anode material and with current densitiesof, for example, up to amps/elm? without the yields being appreciablyreduced. By this means, it is possible to obtain a high transforma tionper unit of time with electrodes of small dimensions.

According to a preferred embodiment of the present invention, thetemperature in the anode space during the oxidation process is keptbelow 50 C., more preferably below C., for which purpose externalcooling may be necessary. When the temperature rises substantially above2,786,022 Ph'teirtd Man 1 9, 1957 "-20C.,- for example to -40" C.,"theyield is lowered as compared withthe yieldswhich are obtainable by using"lower "temperatures. Whereas it is possible, for'example,'underotherwise equal conditions to obtain a yield of 5 about7 2%'ofacetylene dicarboxylic acidwhen'butin-(D- '-diol-1,4 is oxidisedelectrolytically to give the said acetylene dicarboxylic acid, using atemperature range of -about:8 9- C., theyield drops toabout 58% when thesamebpteration is carried out without cooling and the "temperature-inthe anode space rises to 30-40 C.'owing to spontaneousheating. Thislatteryield is still always substantially better than'theyieldwhichcan'be obtained according'tothe known processes. In the interest'ofindustrial' efficiency, however, it is expedient 'to determine 15 1..

particular case.

and observe 'the optimum reaction temperature in each Furthermore,it'has been found thatitis expedient not to's'elect-too high an alcoholconcentration and preferably butin-(2) -diol-1,4 to formacetylenedicarboxylic acid, it

amounts to 'about72% of the theoretical, the yield with \an alcoholconcentration of 10+1l% drops to about' 51%. The yieldof 51'% issubstantially betterthan' th'atwhich canbe produced with thepreviously'kn'ov'vn processes, but -itisnevertheless in the interest ofthe industrial efficiency .30

tration in each particular case.

of thep'ro'cess' to determine the optimum a'lcohol concen- It isexpedient toselect sulphuric acid'as the acid. The influence of thesulphuric acid concentration on the yield is not very pronounced. It ispossible for the sulphuric acid concentration in the anode space tobe-lowered to "about 1% without thereby substantially impairing theyield. On" the other hand, it is not desirable to raise the -sulphuricacid concentration beyond 30%, because the yield then begins to fall bya few percent.

When carrying out the process of the invention, it is only necessary tocover the anode space and provide it with a reflux condenser when thestarting products or intermediate products or endproducts arereadilyvolatile. -It is'also not necessary to move the anode liquid with allacetylene alcohols.

than 70% acid is already obtained with current energypbut the yielddrops gra-dually'when the current energyis more than It is expedient :touselead dioxide anodes. It is also desirable to separate the anode andcathode chambers in a suitable manner.

The present process givescrude products int the form acids of highconcentratiomwhich-are not or areonly slightly contaminated byby-products,gandc-which may he used as such or if desired may be furtherworked up into pure end products. In the case of acetylene dicarboxylicacid, a crude product which is 9195% pure is obtained in the form of alight-yellowish to light-brownish powder. The yields which areobtainable according to the present process are substantially higher,for example in the case of acetylene dicarboxylic acid, than the yieldswhich can be produced by the prior known processes.

Example 1 In a rectangular electrolysis vessel, the anode chamber 18.separated from the cathode chamber by a clay plate as diaphragm. Plateglass sheets, fitted on by means of a 1 the electrolysis.

grease packing, serve to cover the electrode chambers.

V The plates are drilled above the cathode chamber to carry a refluxcondenser through which extends the cable supplying current to a 8 x 16cm. copper plate anode, while a second reflux condenser is arrangedabove the anode chamber, the stem of a mechanically operated agitatorextending through a latter condenser. The two ends of an 8 x 10 mm. leadtube serving as anode also project through the cover of the anodechamber.

flat convolutions, i. e. with an effective surface of 1.0 dmi", in theanode liquid. 50 gm. of 96% propargyl alcohol and 550 gm. of sulphuricacid are disposed in the anode chamber, while the cathode chambercontains 15 sulphuric acid. Water is passed through the refluxcondensers and the anode, so that a temperature of 8.5-9 C. ismaintained in the anode chamber during the electrolysis. Whileconstantly stirring, a current of 4.0 amps. with a terminal voltage of3.2 volts is passed through for 26.9 hours, this corresponding-to 107.6ampere hours=1l2.5% of the theoretical current energy.

'After a few minutes, the lead anode is covered with a distilled offfrom the boiling water bath. The residue is distilled under the vacuumof a water pump on an initially warm and then boiling water bath andproduces 53.25

gm. of a light yellow clear liquid which contains 89.35% of propiolicacid, i. c. 47.6 gm. of a 160% acid 76.l% V of the theoretical. Thecurrent yield is 67.5%.

Example 2 In a rectangular electrolysis vessel, the anode chamber isseparated from the cathode chamber by a clay plate as diaphragm. Thecathode is a copper plate of 8 x 16 0111., which dips into approximately15 sulphuric acid. The anode is a lead tube of 8 x 10 mm. which iscoated by a dioxide layer and is immersed over a length of 63.5

cm.,'laid in flat convolutions, i. c. with an eflective surface of 1.0dm. in the anode liquid. The anode cham- .ber contains 25 gm. of pure,butindiol, dissolved in 510 gm. of water, and 90 gm. of concentratedsulphuric acid. Water flows through the anode, so that a temperature of89 C. is maintained in the anode chamber during the electrolysis. Acurrent of 3.0 amps. with a terminal voltage of 3-4 volts is passedthrough for 26 hours and 36 -minutes, which corresponds to 79.75 amperehours=1l0% of'the theoretical current energy. Towards the end of theelectrolysis, the evolution of gaseous oxygen increases. The anodeliquid is filtered, salted out by addition of .common salt and extractedfor 8 hours with ether. The

extract is dried over calcium chloride, filtered off from the latter andthe solvent distilled off in vacuo. There remain 25.75 gm. of a lightbrown powder with an acid content of 94.75%, i. c. 24.4 gm. of a 100%acid-=- 73.9% of the theoretical. The crude product melts at 169-174 C.with decomposition.

The lead tube is immersed over a length of 63.5 cm., laid in 4 Example 3e The operation is carried out as in- Example 2, but instead of thequantities of 25 gm. of pure butindiol, 510 gm. of water and gm. ofconcentrated sulphuric acid, as indicated in Example 2, there are nowintroduced 10 gm. of hexan-diine-(2.4)-diol-1,6 in 500 gm. of 3%su-lphuric acid. The apparatus is encased in black paper. A current of1.0 amp.==0.01 amp./cm. current density is used. The current is passedthrough for 19.5 hours, which corresponds to 100% of the theoreticalcurrent energy. The anode liquid is extracted for 5 hours with ether.The material extracted is cooled with water, whereupon it becomesdarker. The extract is washed twice with a little water. It isthen driedover calcium chloride, a low temperature being ensured by storing in arefrigerator. The red filtrate is mixed with 5 times the quantity ofpetroleum ether, decanted from the precipitated polymer and againdiluted with petroleum ether to 5 times the volume. In the refrigerator,the acid crystalises into initially pure white crystals, which arediscolourcd to greyish-red crystals in spite of cooling and darkness.The yield is 1.333 gm. of diacetylene dicarboxylic acid in the form ofthe dihydrate and in fact the crude yield has a content of 96.8% ofdihydrate. The yield therefore corresponds to 1.29 gm. of 100%dihydrate: 8.15% of the theoretical.

The crystals darken at -100 C.. and decompose without explosion.

From the filtrate, there is obtained, after strong concentration andprecipitation with petroleum ether, a further 0.531 gm. of a 91%dihydrate=0.483 gm. of

dihydrate=3.05% of the theoretical.

What I claim is:

1. A method of producing acetylene carboxylic acids, comprising thesteps of subjecting an acetylene alcohol in a sulfuric acid solutioncontaining a maximum of 30% sulfuric acid to electrolytic oxidation at acurrent density of up to 10 amps./dm. in an electrolytic cell'suppliedwith lead dioxide anodes and having separate anode and cathodecompartments and at a temperature of below 20 C., the concentration ofsaid acetylene alcohol in said acid solution being between 4-25%,thereby converting said acetylene alcohol to the corresponding acetylenecar boxylic acid; and recovering said acetylene carboxylic acid.

2. method of producing acetylene carboxylic acids, comprising the stepsof subjecting butin-(2)-diol-1,4 in

.a sulfpric acid solution containing a maximum of 30% Slllflll'lC acidto electrolytic oxidation at a current density of up to 10 amps./dm. inan electrolytic cell supplied with lead dioxide anodes and havingseparate anode and cathode compartments and at a temperature of below 20C., the concentration of said butin-(2)-diol-1,4 in said acid solutionbeing between 425%, thereby converting said butin-(2)-diol-1,4 to thecorresponding acetylene carboxylic acid; and recovering said acetylenecarboxylic acid.

References Cited in the file of this patent

1. METHOD OF PRODUCING ACETYLENE CARBOXYLIC ACIDS, COMPRISING THE STEPSOF SUBJECTING AN ACETYLENE ALCOHOL IN A SULFURIC ACID SOLUTIONCONTAINING A MAXINUM OF 30% SULFURIC ACID TO ELECTROLYTIC OXIDATION AT ACURRENT DENSITY OF UP TO 10 AMPS./DM.2 IN AN ELECTROLYTIC CELL SUPPLIEDWITH LEAD DIOXIDE ANODES AND HAVING SEPARATE ANODE AND CATHODECOMPARTMENTS AND AT A TEMPERATURE OF BELOW 20 C., THE CONCENTRATION OFSAID ACETYLENE ALCOHOL IN SAID ACID SOLUTION BEING BETWEEN 4-25%,THEREBY CONVERTING SAID ACETYLENE ALCOHOL TO THE CORRESPONDING ACETYLENECARBOXYLIC ACID; AND RECOVERING SAID ACETYLENE CARBOXYLIC ACID.